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Publications

2010

Astrophysics and Astronomy

Articles 1 - 24 of 24

Full-Text Articles in Physical Sciences and Mathematics

Gravity Couplings In The Standard-Model Extension, Quentin G. Bailey Dec 2010

Gravity Couplings In The Standard-Model Extension, Quentin G. Bailey

Publications

The Standard-Model Extension (SME) is an action-based expansion describing general Lorentz violation for known matter and fields, including gravity. In this talk, I will discuss the Lorentz-violating gravity couplings in the SME. Toy models that match the SME expansion, including vector and two-tensor models, are reviewed. Finally I discuss the status of experiments and observations probing gravity coefficients for Lorentz violation.

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Book Review: Stars Above, Earth Below: A Guide To Astronomy In The National Parks, T. D. Oswalt Nov 2010

Book Review: Stars Above, Earth Below: A Guide To Astronomy In The National Parks, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Stars Above, Earth Below : a Guide to Astronomy in the National Parks by Tyler Nordgren. Springer/Praxis, 2010 444p, 9781441916488 $29.95.

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New Tests Of General Relativity, Quentin Bailey Oct 2010

New Tests Of General Relativity, Quentin Bailey

Publications

The last decade has seen a rapid increase in the number of precision tests of relativity. This research has been motivated by the intriguing possibility that tiny deviations from relativity might arise in the underlying theory that is widely believed to successfully mesh General Relativity (GR) with quantum physics. Many of these tests have been analyzed within an effective field theory framework which generically describes possible deviations from exact relativity and contains some traditional test frameworks as limiting cases. One part of the activity has been a resurgence of interest in tests of relativity in the Minkowski-spacetime context, where Lorentz …

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Probing The Evolving Massive Star Population In Orion With Kinematic And Radioactive Tracers, R. Voss, R. Diehl, J. S. Vink, Dieter H. Hartmann Sep 2010

Probing The Evolving Massive Star Population In Orion With Kinematic And Radioactive Tracers, R. Voss, R. Diehl, J. S. Vink, Dieter H. Hartmann

Publications

Context. Orion is the nearest star-forming region to host a significant number of young and massive stars. The energy injected by these OB stars is thought to have created the Eridanus superbubble. Because of its proximity, Orion is a prime target for a detailed investigation of the interaction between massive stars and their environment. Aims. We study the massive star population of Orion and its feedback in terms of energy and mass, in order to compare the current knowledge of massive stars with kinematic and radioactive tracers in the surrounding interstellar medium (ISM). Methods. We assembled a census of the …

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A Detailed Model Atmosphere Analysis Of Cool White Dwarfs In The Sloan Digital Sky Survey, Mukremin Kilic, Ted Von Hippel, Et Al. Sep 2010

A Detailed Model Atmosphere Analysis Of Cool White Dwarfs In The Sloan Digital Sky Survey, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We present optical spectroscopy and near-infrared photometry of 126 cool white dwarfs (WDs) in the Sloan Digital Sky Survey (SDSS). Our sample includes high proper motion targets selected using the SDSS and USNO-B astrometry and a dozen previously known ultracool WD candidates. Our optical spectroscopic observations demonstrate that a clean selection of large samples of cool WDs in the SDSS (and the SkyMapper, Pan-STARRS, and the Large Synoptic Survey Telescope data sets) is possible using a reduced proper motion diagram and a tangential velocity cut-off (depending on the proper motion accuracy) of 30 km s–1. Our near-infrared observations reveal eight …

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Monster In The Dark: The Ultraluminous Grb 080607 And Its Dusty Environment, Dieter H. Hartmann, D. A. Perley, A. N. Morgan, A. Updike, F. Yuan, C. W. Awkerlof, A. A. Miller, J. S. Bloom, S. B. Cenko, W. Li Aug 2010

Monster In The Dark: The Ultraluminous Grb 080607 And Its Dusty Environment, Dieter H. Hartmann, D. A. Perley, A. N. Morgan, A. Updike, F. Yuan, C. W. Awkerlof, A. A. Miller, J. S. Bloom, S. B. Cenko, W. Li

Publications

We present early-time optical through infrared photometry of the bright gamma-ray burst GRB 080607, starting only 6 s following the initial trigger in the rest frame. Complemented by our previously published spectroscopy, this high-quality photometric dataset allows us to solve for the extinction properties of the redshift 3.036 sightline, giving perhaps the most detailed information on the ultraviolet continuum absorption properties of any sightline outside our Local Group to date. The extinction properties are not adequately modeled by any ordinary extinction template (including the average Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud curves), partially because the 2175 A …

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Locating The Accretion Footprint On A Herbig Ae Star: Mwc 480, C A. Grady, K Hamaguchi, G Schneider, B Stecklum, B E. Woodgate, J E. Mccleary, G M. Williger, M L. Sitko, F Menard, Th. Henning, Sean D. Brittain Aug 2010

Locating The Accretion Footprint On A Herbig Ae Star: Mwc 480, C A. Grady, K Hamaguchi, G Schneider, B Stecklum, B E. Woodgate, J E. Mccleary, G M. Williger, M L. Sitko, F Menard, Th. Henning, Sean D. Brittain

Publications

Accretion is a fundamental process which establishes the dynamics of the protoplanetary disk and the final properties of the forming star. In solar-type stars, the star–disk coupling is determined by the magnetic field structure, which is responsible for funneling material from the disk midplane to higher latitudes on the star. Here, we use pan-chromatic data for the Herbig Ae star MWC 480 to address whether similar processes occur in intermediatemass stars. MWC 480 has X-ray emission typical of actively accreting Herbig Ae stars, but with ∼10× more photoelectric absorption than expected from optical and FUV data. We consider three sources …

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Spectroscopic Abundances And Membership In The Wolf 630 Moving Group, Eric J. Bubar, Jeremy R. King Aug 2010

Spectroscopic Abundances And Membership In The Wolf 630 Moving Group, Eric J. Bubar, Jeremy R. King

Publications

The concept of kinematic assemblages evolving from dispersed stellar clusters has remained contentious since Eggen’s initial formulation of moving groups in the 1960s. With high-quality parallaxes from the Hipparcos space astrometry mission, distance measurements for thousands of nearby, seemingly isolated stars are currently available. With these distances, a high-resolution spectroscopic abundance analysis can be brought to bear on the alleged members of these moving groups. If a structure is a relic of an open cluster, the members can be expected to be monolithic in age and abundance in as much as homogeneity is observed in young open clusters. In this …

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Evidence For The Supernova-Synthesized Dust From The Rising Afterglow Of Grb071025 At Z ∼ 5, Daniel A. Perley, J. S. Bloom, C. R. Klein, S. Covino, T. Minezaki, P. Wozniak, W. T. Vestrand, G. G. Williams, P. Milne, N R. Butler, A C. Updike, T Kruhler, P Afonso, A Antonelli, L Cowie, P Ferrero, J Greiner, Dieter H. Hartmann, Y Kakazu, A Küpcü Yoldaş, A N. Morgan, P A. Price, J X. Prochaska, Y Yoshii Jul 2010

Evidence For The Supernova-Synthesized Dust From The Rising Afterglow Of Grb071025 At Z ∼ 5, Daniel A. Perley, J. S. Bloom, C. R. Klein, S. Covino, T. Minezaki, P. Wozniak, W. T. Vestrand, G. G. Williams, P. Milne, N R. Butler, A C. Updike, T Kruhler, P Afonso, A Antonelli, L Cowie, P Ferrero, J Greiner, Dieter H. Hartmann, Y Kakazu, A Küpcü Yoldaş, A N. Morgan, P A. Price, J X. Prochaska, Y Yoshii

Publications

We present observations and analysis of the broad-band afterglow of Swift GRB 071025. Using optical and infrared (RIYJHK) photometry, we derive a photometric redshift of 4.4 < 5.2; at this redshift our simultaneous multicolour observations begin at ∼30 s after the gamma-ray burst trigger in the host frame, during the initial rising phase of the afterglow. We associate the light-curve peak at ∼580 s in the observer frame with the formation of the forward shock, giving an estimate of the initial Lorentz factor 0 ∼ 200. The red spectral energy distribution (even in regions not affected by the Lyman α break) provides secure evidence of a large dust column. However, the inferred extinction curve shows a prominent flat component between 2000 and 3000 Å in the rest frame, inconsistent with any locally observed template but well fitted by models of dust formed by supernovae. Time-dependent fits to the extinction profile reveal no evidence of dust destruction and limit the decrease in the extinction column to A3000 < 0.54 mag after t = 50 s in the rest frame. Together with studies of high-z quasars, our observations suggest a transition in dust properties in the early Universe, possibly associated with a transition between supernova-dominated and asymptotic giant branch-dominated modes of dust production.

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Modeling Gas Distribution In Protoplanetary Accretion Disks, Martin Kronberg, Josiah Lewis, Sean D. Brittain Jul 2010

Modeling Gas Distribution In Protoplanetary Accretion Disks, Martin Kronberg, Josiah Lewis, Sean D. Brittain

Publications

Protoplanetary accretion disks are disks of dust and gas which surround and feed material onto a forming star in the earliest stages of its evolution. One of the most useful methods for studying these disks is near infrared spectroscopy of rovibrational CO emission. This paper presents the methods in which synthetically generated spectra are modeled and fit to spectral data gathered from protoplanetary disks. This paper also discussed the methods in which this code can be improved by modifying the code to run a Monte Carlo analysis of best fit across the CONDOR cluster at Clemson University, thereby allowing for …

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Probing Protoplanetary Disk Upper Atmospheres For Heating And Dust Settling Using Synthetic Co Spectra, Josiah Lewis, Martin Kronberg, Sean D. Brittain Jul 2010

Probing Protoplanetary Disk Upper Atmospheres For Heating And Dust Settling Using Synthetic Co Spectra, Josiah Lewis, Martin Kronberg, Sean D. Brittain

Publications

CO emission is a useful probe of the warm gas distribution in the planet forming regions of disks around Herbig Ae/Be (HAeBe) stars. We model UV fluoresced and thermally excited CO in the circumstellar disks of several HAeBes. We find indications of dust settling in the upper atmospheres of HD 141569 and HD 97048 and a correlation between PAH luminosity and gas heating in these two systems.

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Gas In The Protoplanetary Disc Of Hd 169142: Herschel's View, G Meeus, C Pinte, P Woitke, B Montesinos, I Mendigutia, P Riviere-Marichalar, C Eiroa, G S. Mathews, B Vandenbussche, C D. Howard, A Roberge, G Sandell, G Duchene, F Menard, C A. Grady, W.R.F. Dent, I Kamp, J C. Augereau, W F. Thi, I Tilling, J M. Alacid, S Andrews, D R. Ardila, G Aresu, D Barrado, Sean D. Brittain Jul 2010

Gas In The Protoplanetary Disc Of Hd 169142: Herschel's View, G Meeus, C Pinte, P Woitke, B Montesinos, I Mendigutia, P Riviere-Marichalar, C Eiroa, G S. Mathews, B Vandenbussche, C D. Howard, A Roberge, G Sandell, G Duchene, F Menard, C A. Grady, W.R.F. Dent, I Kamp, J C. Augereau, W F. Thi, I Tilling, J M. Alacid, S Andrews, D R. Ardila, G Aresu, D Barrado, Sean D. Brittain

Publications

In an effort to simultaneously study the gas and dust components of the disc surrounding the young Herbig Ae star HD 169142, we present far-IR observations obtained with the PACS instrument onboard the Herschel Space Observatory. This work is part of the open time key program GASPS, which is aimed at studying the evolution of protoplanetary discs. To constrain the gas properties in the outer disc, we observed the star at several key gas-lines, including [OI] 63.2 and 145.5 mum, [CII] 157.7 mum, CO 72.8 and 90.2 mum, and o-H2O 78.7 and 179.5 mum. We only detect the [OI] 63.2 …

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Herschel-Pacs Observation Of The 10 Myr Old T Tauri Disk Tw Hya. Constraining The Disk Gas Mass, W F. Thi, G Mathews, F Menard, P Woitke, G Meeus, P Riviere-Marichalar, C Pinte, C D. Howard, A Roberge, G Sandell, I Pascucci, B Riaz, C A. Grady, W.R.F. Dent, I Kamp, G Duchene, J.-C. Augereau, E Pantin, B Vandenbussche, I Tilling, J P. Williams, C Eiroa, D Barrado, J M. Alacid, S Andrews, D R. Ardila, G Aresu, Sean D. Brittain, D R. Ciardi, W Danchi Jul 2010

Herschel-Pacs Observation Of The 10 Myr Old T Tauri Disk Tw Hya. Constraining The Disk Gas Mass, W F. Thi, G Mathews, F Menard, P Woitke, G Meeus, P Riviere-Marichalar, C Pinte, C D. Howard, A Roberge, G Sandell, I Pascucci, B Riaz, C A. Grady, W.R.F. Dent, I Kamp, G Duchene, J.-C. Augereau, E Pantin, B Vandenbussche, I Tilling, J P. Williams, C Eiroa, D Barrado, J M. Alacid, S Andrews, D R. Ardila, G Aresu, Sean D. Brittain, D R. Ciardi, W Danchi

Publications

Planets are formed in disks around young stars. With an age of ~10 Myr, TW Hya is one of the nearest T Tauri stars that is still surrounded by a relatively massive disk. In addition a large number of molecules has been found in the TW Hya disk, making TW Hya the perfect test case in a large survey of disks with Herschel–PACS to directly study their gaseous component. We aim to constrain the gas and dust mass of the circumstellar disk around TW Hya. We observed the fine-structure lines of [O i] and [C ii] as part of the …

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Application Of Asymptotic Expansions For Maximum Likelihood Estimators Errors To Gravitational Waves From Binary Mergers: The Single Interferometer Case, M. Zanolin, S. Vitale, N. Makris Jun 2010

Application Of Asymptotic Expansions For Maximum Likelihood Estimators Errors To Gravitational Waves From Binary Mergers: The Single Interferometer Case, M. Zanolin, S. Vitale, N. Makris

Publications

In this paper we describe a new methodology to calculate analytically the error for a maximum likelihood estimate (MLE) for physical parameters from gravitational wave signals. All the existing literature focuses on the usage of the Cramer Rao Lower bounds (CRLB) as a mean to approximate the errors for large signal to noise ratios. We show here how the variance and the bias of an MLE estimate can be expressed instead in inverse powers of the signal to noise ratios where the first order in the variance expansion is the CRLB. As an application we compute the second order of …

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Visitors From The Halo: 11 Gyr Old White Dwarfs In The Solar Neighborhood, Mukremin Kilic, Ted Von Hippel, Et Al. May 2010

Visitors From The Halo: 11 Gyr Old White Dwarfs In The Solar Neighborhood, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We report the discovery of three nearby old halo white dwarf (WD) candidates in the Sloan Digital Sky Survey (SDSS), including two stars in a common proper motion binary system. These candidates are selected from our 2800deg2 proper motion survey on the Bok and U.S. Naval Observatory Flagstaff Station 1.3 m telescopes, and they display proper motions of 0˝.4-0˝.5 yr¯1. Follow-up MMT spectroscopy and near-infrared photometry demonstrate that all three objects are hydrogen-dominated atmosphere WDs with T eff ≈ 3700-4100 K. For average mass WDs, these temperature estimates correspond to cooling ages of 9-10 Gyr, distances of 70-80 pc, and …

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Fe I And Fe Ii Abundances Of Solar-Type Dwarfs In The Pleiades Open Cluster, Simon C. Schuler, Adele L. Plunkett, Jeremy R. King, Marc H. Pinsonneault May 2010

Fe I And Fe Ii Abundances Of Solar-Type Dwarfs In The Pleiades Open Cluster, Simon C. Schuler, Adele L. Plunkett, Jeremy R. King, Marc H. Pinsonneault

Publications

We have derived Fe abundances of 16 solar-type Pleiades dwarfs by means of an equivalent width analysis of Fe I and Fe II lines in high-resolution spectra obtained with the Hobby - Eberly Telescope and High Resolution Spectrograph. Abundances derived from Fe II lines are larger than those derived from Fe I lines (herein referred to as over-ionization) for stars with Teff < 5400 K, and the dis-crepancy (∆Fe = [Fe II/H] - [Fe I/H]) increases dramatically with decreasing Teff, reaching over 0.8 dex for the coolest stars of our sample. The Pleiades joins the open clusters M34, the Hyades, IC2602, and IC2391, and the Ursa Major moving group, demonstrating ostensible over-ionization trends. The Pleiades ∆Fe abun-dances are correlated with Ca II infrared triplet and Hα chromospheric emission indicators and relative differences therein. Oxygen abundances of our Pleiades sample derived from the high-excitation O I triplet have been previously shown to increase with decreasing Teff, and a comparison with the ∆Fe abundances sug-gests that the over-excitation (larger abundances derived from high excitation lines relative to low excitation lines) and over-ionization effects that have been observed in cool open cluster and disk field main sequence (MS) dwarfs share a common origin. Curiously, a correlation between the Pleiades O I abundances and chromospheric emission indicators does not exist. Star-to-star Fe I abun-dances have low internal scatter (< 0.11 dex), but the abundances of stars with Teff< 5400 K are systematically higher compared to the warmer stars. The cool star [Fe I/H] abundances cannot be connected directly to over-excitation effects, but similarities with the ∆Fe and O I triplet trends suggest the abundances are dubious. Using the [Fe I/H] abundances of five stars with Teff > 5400 K, we derive a mean Pleiades cluster metallicity of [Fe/H] = +0.01 ± 0.02.

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Co And H+3 Toward Mwc 1080, Mwc 349, And Lkhα 101, E L. Gibb, Sean D. Brittain, T W. Rettig, M Troutman, Theodore Simon, C Kulesa May 2010

Co And H+3 Toward Mwc 1080, Mwc 349, And Lkhα 101, E L. Gibb, Sean D. Brittain, T W. Rettig, M Troutman, Theodore Simon, C Kulesa

Publications

We present high-resolution, near-infrared NIRSPEC observations of the fundamental rovibrational CO and H+ 3 R(1,0), R(1,1) u , and Q(1,0) transitions toward three early-type young stars: MWC 1080, MWC 349, and LkHα 101. These observations were performed for the purpose of constraining the physical characteristics of the interstellar material along each line of sight. Toward MWC 1080, we detected strong CO absorption and determined a column density upper limit of 1.4 × 1014 cm–2 for H+ 3. We infer that there is very little diffuse material along the line of sight toward MWC 1080 and that the CO absorption is …

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Pulsational Mapping Of Calcium Across The Surface Of A White Dwarf, Susan E. Thompson, Ted Von Hippel, Et Al. May 2010

Pulsational Mapping Of Calcium Across The Surface Of A White Dwarf, Susan E. Thompson, Ted Von Hippel, Et Al.

Publications

We constrain the distribution of calcium across the surface of the white dwarf star G29-38 by combining time-series spectroscopy from Gemini-North with global time-series photometry from the Whole Earth Telescope. G29-38 is actively accreting metals from a known debris disk. Since the metals sink significantly faster than they mix across the surface, any inhomogeneity in the accretion process will appear as an inhomogeneity of the metals on the surface of the star. We measure the flux amplitudes and the calcium equivalent width amplitudes for two large pulsations excited on G29-38 in 2008. The ratio of these amplitudes best fits a …

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Lorentz Violation And Gravity, Quentin G. Bailey Apr 2010

Lorentz Violation And Gravity, Quentin G. Bailey

Publications

In the last decade, a variety of high-precision experiments have searched for miniscule violations of Lorentz symmetry. These searches are largely motivated by the possibility of uncovering experimental signatures from a fundamental unified theory. Experimental results are reported in the framework called the Standard-Model Extension (SME), which describes general Lorentz violation for each particle species in terms of its coefficients for Lorentz violation. Recently, the role of gravitational experiments in probing the SME has been explored in the literature. In this talk, I will summarize theoretical and experimental aspects of these works. I will also discuss recent lunar laser ranging …

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The Equivalence Principle, Uniformly Accelerated Reference Frames, And The Uniform Gravitational Field, Gerardo Muñoz, Preston Jones Mar 2010

The Equivalence Principle, Uniformly Accelerated Reference Frames, And The Uniform Gravitational Field, Gerardo Muñoz, Preston Jones

Publications

The relation between uniformly accelerated reference frames in flat spacetime and the uniform gravitational field is examined in a relativistic context. It is shown that contrary to previous statements, equivalence does not break down in this context. No restrictions to Newtonian approximations or small enclosures are necessary.

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Recent Discoveries Of Supersoft X-Ray Sources In M 31, M. Henze, W. Pietsch, E. Haberl, G. Sala, M. Hernanz, D. Hartzidimitriou, A. Rau, Dieter H. Hartmann, J. Greiner, M. Orio, H Stiele, M.J. Freyberg Feb 2010

Recent Discoveries Of Supersoft X-Ray Sources In M 31, M. Henze, W. Pietsch, E. Haberl, G. Sala, M. Hernanz, D. Hartzidimitriou, A. Rau, Dieter H. Hartmann, J. Greiner, M. Orio, H Stiele, M.J. Freyberg

Publications

Classical novae (CNe) have recently been reported to represent the major class of supersoft X-ray sources (SSSs) in the central area of our neighbouring galaxy M 31. This paper presents a review of results from recent X-ray observations of M 31 with XMM-Newton and Chandra. We carried out a dedicated optical and X-ray monitoring program of CNe and SSSs in the central area of M 31. We discovered the first SSSs in M 31 globular clusters (GCs) and their connection to the very first discovered CN in a M 31 GC. This result may have an impact on the CN …

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Dual Gamma-Ray Mission, S. Boggs, C. Wunderer, P. Von Ballmoos, T. Takahashi, N. Gehrels, J. Tueller, M. Baring, J. Beacom, R. Diehl, J Greiner, E Grove, Dieter H. Hartmann Jan 2010

Dual Gamma-Ray Mission, S. Boggs, C. Wunderer, P. Von Ballmoos, T. Takahashi, N. Gehrels, J. Tueller, M. Baring, J. Beacom, R. Diehl, J Greiner, E Grove, Dieter H. Hartmann

Publications

Gamma-rays at MeV energies provide a unique window on the high energy Universe, especially so for nuclear astrophysics. The potential for significant contributions, e.g., to the understanding of SNe Ia as well as the large potential for new discoveries has long been recognized, but technical progress in this challenging energy band has been slow. The groundbreaking discoveries of CGRO’s COMPTEL, however, have inspired and driven the development of powerful new instrumentation over the past decade. Novel detector technologies developed in the US and Japan enable compact Compton telescopes, greatly improving the efficiency and field-of-view achievable with this technique successfully employed …

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The Dynamic X-Ray Sky Of The Local Universe, S. Boggs, C. Wunderer, P. Von Ballmoos, T. Takahashi, N. Gehrels, J. Tueller, M. Baring, J. Beacom, R. Diehl, Dieter H. Hartmann Jan 2010

The Dynamic X-Ray Sky Of The Local Universe, S. Boggs, C. Wunderer, P. Von Ballmoos, T. Takahashi, N. Gehrels, J. Tueller, M. Baring, J. Beacom, R. Diehl, Dieter H. Hartmann

Publications

Over the next decade, we can expect time domain astronomy to flourish at optical and radio wavelengths. In parallel with these efforts, a dedicated transient "machine" operating at higher energies (X-ray band through soft gamma-rays) is required to reveal the unique subset of events with variable emission predominantly visible above 100 eV. Here we focus on the transient phase space never yet sampled due to the lack of a sensitive, wide-field and triggering facility dedicated exclusively to catching high energy transients and enabling rapid coordinated multi-wavelength follow-up. We first describe the advancements in our understanding of known X-ray transients that …

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On The Origin Of The Highest Redshift Gamma-Ray Bursts, Krzysztof Belczynski, Daniel E. Holz, Chris L. Fryer, Edo Berger, Dieter H. Hartmann, Brain O'Shea Jan 2010

On The Origin Of The Highest Redshift Gamma-Ray Bursts, Krzysztof Belczynski, Daniel E. Holz, Chris L. Fryer, Edo Berger, Dieter H. Hartmann, Brain O'Shea

Publications

GRB 080913 and GRB 090423 are the most distant gamma-ray bursts (GRBs) known to date, with spectroscop-ically determined redshifts of z = 6.7 and z = 8.1, respectively. The detection of bursts at this early epoch of the universe significantly constrains the nature of GRBs and their progenitors. We perform population synthesis studies of the formation and evolution of early stars, and calculate the resulting formation rates of short- and long-duration GRBs at high redshift. The peak of the GRB rate from Population II stars occurs at z ∼ 7for a model with efficient/fast mixing of metals, while it is …

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